Peripheral artery disease (PAD) is associated with vascular obstructions in the extremities, leading to intermit tentclaudication, ischemic ulcers, leg pain at rest, and amputation. In the US, approximately 6.5 million people have peripheral artery disease (PAD),affecting 12-20% of people over 60 years of age. Current cell therapies to restore limb perfusion have shown only moderate benefits due to poor transplant cell survival and inadequate pro-angiogenic cues. Therefore, there is a critical need for alternative treatments for PAD therapy. Recently, therapy using mesenchymal stem cell (MSCs)-derived exosomes has been recognized as a promising, cell-free treatment in various diseases, including PAD. However, MSCs are heterogeneous and do not scale well, thus, limiting their usefulness as a reliable source of exosomes for commercial scale development and clinical application. We at AgeX Therapeutics have previously shown that our highly regenerative, proprietary PureStem® progenitor cells, which are at an early developmental state, produce highly angiogenic exosomes. Thus, we propose to overcome the current exosome production limitations by using AgeX's highly scalable PureStem® human pluripotent stem cell-derived cell lines as a source of allogeneic PAD therapy. A key rationale for using exosomes is that they have low immunogenicity, which means they are not likely to cause undesirable immune responses, and they are non-replicative, which obviates many of the risks associated with cell therapy. Since exosomes mediate intercellular communication, instead of administering cells, we can use PureStem angiogenic exosomes in a murine model of PAD to improve limb revascularization and blood perfusion. Moreover, exosomes are likely to be more cost-effective to produce and more convenient to use and store. The goal of this STTR Phase I proposal is to demonstrate the therapeutic feasibility of exosomes to improve angiogenic function in a mouse hind limb ischemia model. First, we will establish two lead angiogenic exosome production cell lines and produce GMP-compatible PureStem® exosomes in vitro by assessing lines based onexosome output, exosome angiogenic activity, and exosome scalability and stability. We will then test the two selected PureStem exosome lines in a hind limb ischemia mouse model to validate their therapeutic efficacy invivo. Evidence of in vivo feasibility in our well-established PAD animal model using exosomes from a scalable PureStem cell line will pave the way for further preclinical development and IND, thus enabling studies for a prospective STTR Phase II. Taken together, we anticipate the therapeutic potential for PureStem exosomes to provide an innovative, cost-effective, and convenient "off-the-shelf" regenerative stem cell-derived therapy for PAD.
Public Health Relevance Statement: NARRATIVE: Peripheral artery disease (PAD) is characterized by narrowing of the arteries which leads to insufficient blood flow to the arms and legs, resulting in reduced oxygen in the affected areas (known as tissue ischemia). In the US, approximately 6.5 million people have PAD, affecting 12-20% of people over 60 years of age . Thus, we propose to employ exosomes, extracellular vesicles (size of 30-120nm) which can improve blood flow and formation of new vessels (known as angiogenesis) after ischemia has occurred. Exosomes are promising therapeutic agents because they are non-replicative and have low immunogenicity, which means they are not likely to cause undesirable immune responses. We have previously developed exosomes derived from AgeX's clonally pure PureStem® progenitor stem cell lines, which have a high degree of homogeneity (i.e., purity) and are highly proliferative and regenerative. The goal of this Phase I proposal is to demonstrate feasibility by selecting candidate exosome production cell lines from our library and demonstrating efficacy of candidate exosomes on improvement of angiogenic outcomes in a clinically relevant PAD animal model of hind limb ischemia.
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